A “legacy” game, where your contributions to the game continue even if you’re logged off, meted with an mmorpg
It could be anything, but my idea is something like cities:skylines. Interconnected cities or areas each with a mayor or admins that direct the goals of the area..
Then the 2nd aspect of the game is more like GTA, where people interact with the areas.
The areas could be like San Andreas, but then you could walk to the edge and it becomes more like a village from Warcraft. Or maybe an area is filled with ghosts and most of the goals in the area are delivering packages. Or maybe there’s an area like Sanctum 2, fallout, or any other idea. It would be up to the admins/mayors to figure out how to design it.
The game would fill in gaps in city creation for random encounters, etc. the in-game players actions would have some effect on the area itself.
I would expect the game to support itself through a combination of ads and subs. Companies could pay to have more control over what advertising exists in their area.